When the laud lies on a dry subsoil, and no more moisture remains in it, after continued rains, than is useful to promote vegetation, it may be ploughed quite flat. This may be (lone by a plough with a moveable turn-furrow, or by ploughing in very great widths. The best way is to draw a furrow the whole length of the field in the middle, and plough towards this from both sides. If the field is wide, it is most convenient to plough it into several broad stitches, each a certain number of perches in breadth. A perch (16i feet) is a very common width for a " stitch," and convenient to guide the sower or the drilling machine.
On wet undrained soils it is necessary to lay the land in a rounded form, in order to let the superfluous water run off into furrows, from which it is conducted by proper channels into the ditches. In this case half a perch is a common width for each stitch, or land, as it is sometimes called. It requires some practice to lay up a land 'in a rounded form from a flat surface. After crosa-ploughiug and harrowing, the first furrow is drawn wide and shallow, and the earth is thrown upon the surface to the right : when the plough returns, it takes another furrow about nine or ten inches from the first, laying the earth or furrow-slice somewhat obliquely over the first. At the next turn another slice is laid, meeting the last at an angle, the first slice being quite covered by the two last. This now forms the crown of the ridge ; and the succeeding slices are laid obliquely, leaning to the right and left till the required width is obtained. Another land is now begun at the distance of a quarter of a perch from the last furrow, and laid exactly in the same manuer. When the two lands meet, the intervening furrow, which had been purposely left shallower, is deepened ; and there is a furrow between every two lands, the bottom of which is considerably below the bottom of the other furrows. When this field is ploughed again after harvest, the work is reversed ; the furrow between the lands is filled with the first slice, and another is placed over this, which now becomes the crown of the land to be formed : this is called ploughing crown and furrow. When the lands are ploughed towards the crown, it is called gathering. By gathering several times in succession, the soil is much raised at the crown at the expense of the sides. This was the old practice, when lands were laid very wide and very high ; in common fields, the land or stitch was often the whole width of the possession, from which came the name of land. In Scotland they are called riggs.
One of the most useful operations in ploughing land is to cross the former furrows, by which means the whole soil is much more com pletely stirred ; and if any part has been left solid without being moved by the plough-share, which is called a balk, it is now necessarily moved. The leaving of balks is a great fault, and is owing to the sole of the plough being narrower than the furrow-slice, and the wing of the point too short, or to the ploughman not holding his plough upright.
The share should cut the ground to the whole width of the furrow, that no roots of thistles, docks, or other large weeds may escape and grow up again. The Roman authors recommended the use of a sharp rod or stake inserted horizontally into the ground, to discover if there were any balks, which, with their ploughs, must have been often left, if the ploughman was not very careful to make close and small furrows. Many ploughmen hold the plough in an oblique position ; the bottom of the furrow is consequently not level, and the soil is not stirred equally. This is a great fault, especially in wet ground ; for the furrows thus become channels in which the water remains, not being able to run over the inequalities of the bottom. It is of no use to lay the surface couvex, if the solid earth below lies In hollows or gutters. The water naturally sinks down into the newly-ploughed land, and if it be undrained it sinks only till it meets the solid bottom which the plough has gone over ; if it can run over this into the deeper furrows between the stitches, it evaporates or runs off, and the land is left dry, and so consolidated as to let the water run along the surface without sinking to any depth ; bnt if the bottom is uneven, it remains in the hollows, and stagnates there, to the great injury of the growing crops.
There are various modes of ploughing land when it is intended to pulverise and expose it to the sun in summer, or the frost in winter, to purify and fertilise it. To expose as great a surface as possible, the whole field is laid in high and narrow ridges, bringing to the surface all the fertile portion of the soil, and often also a portion of the subsoil so as to deepen the productive portion and give more room for the roots to spread in. The simplest method of increasing the surface exposed, when the land is first broken up from pasture, or after having been some years in grass, and is in a foul state, is called ribbing, or "coffering." The plough turns up a slice, which it lays over flat on the adjoining surface. It does not cover this with the next slice, as if it were beginning the crown of a stitch, but it takes another slice at some distance, and then one parallel to the first, like wiso laid flat on the solid part. When the whole field has been so ploughed, the surface consists altogether of ridges and furrows ; but only half the surface has been ploughed. No grass appears, if it has been well done, the unploughed strips being covered by the slices raised by the side of them, the two surfaces with grans on them cover each other. It is left in this state till the grass is rotten, and when the sod is broken to pieces by heavy drag-harrows, the land can be cross-ploughed and cleaned or followed in dry weather.